Electromagnetic driving mechanism



March 1949- s. E. CHRISTIANSEN 2,465,193

ELECTROMAGNETIC DRIVING MECHANISM Filed May, 9, 1945 SENDING l/JY/T(ling/ Ina Patented Mar. 22, 1949 ELECTROMAGNETIC DRIVING MECHANISMSoren E. Christlansen, Great Neck, N. Y., assignor to Stewart-WarnerCorporation, Chicago, Ill., a corporation of Virginia Application May 9,1945, Serial No. 592,781

3 Claims. (c1. 74-142) 1 My invention relates generally toelectromagnetic driving mechanisms, and more particularly to means forrotating a part in synchronism with a remotely located apparatus sendingelectrical pulses to the mechanism.

The invention is herein illustrated "as applied to an odometer drive. Ithas been proposed to drive odometers on vehicles electromagnetically,using a cam on, or driven by, the propeller shaft to close a switch uponeach revolution, or a given number of revolutions, of a shaft. Thisswitch completes a circuit through an electromagnet arranged with a pawlto rotate a ratchet wheel. In such mechanisms it has been conventionaltohave the armature of the electromagnet operate the pawl when theelectromagnet is energized and to return the armature by means of aspring. In such arrangements the rapidity of the operating stroke of thearmature varied with the voltage of the source of current. Inautomobiles, the operating voltage may vary considerably, depending uponthe condition of the generator, the battery, and the relay mechanismcontrolling the charging of the battery, as well as upon the I load onthe electrical system.

The variations in the speed of movement of the armature made itpossible, under high voltage conditions, for the pawl to overdrive theratchet wheel, due to inertia of the moving parts. It also made itnecessary that the electromagnet be relatively powerful, since, whenenergized, it not only had to operate the ratchet wheel, but also toovercome the force of the armature return spring.

In accordance with the principles of my invention, these disadvantagesof the prior mechanisms are overcome, and it is therefore the primaryobject of my invention to provide an improved electromagnetic drivingmechanism for converting electrical pulse energy into rotary motion.

A further object is to provide an electromagnetic driving mechanismwhich utilizes a minimum amount of power, the operation of which is notaffected by substantial variation in the voltage of the pulses, andwhich will be eflicient and reliable in operation.

Other objects will appear from the following description, referencebeing had to the accompanying drawings, in which:

Fig. 1 is an elevational view of the driving mechanism showing the partsin an intermediate position;

Fig. 2 is a similar view, showing the parts in the positions assumed asthe armature has completed its stroke toward the electromagnet; and

Fig. 3 is a similar view showing the'parts in their normal positions.

The invention is illustrated as an odometer drive, the odometer notbeing shown in detail but being driven by a shaft l0 to-which a ratchetwheel I2 is secured. The odometer may be of any well known construction.The shaft l0 projects through a mounting plate I4 of the odometer frame.A holding pawl or dog It is pivoted on plate H, the pawl being heldagainst the ratchet wheel by a light spring l8. An .electromagnetcomprising a U-shaped core "having a winding 22 is suitably mounted onthe plate l4. A soft iron armature 24 is pivoted on a stud 26 mounted onthe plate [4, and has a long leaf spring pawl-28 riveted thereto at apoint near the armature pivot. An adjustable stop 30 limits the upwardmovement of the armature 24, while a similar adjustable stop 32 having arubber cap 34 limits the downward movement of the armature. A helicalcoil spring 36 has one end hooked to the end of the leaf spring pawl 28and has its other end anchored on a stud 38 projecting from the mountingplate I4. I

The downward movement of the, leaf spring pawl 28 is limited by anadjustable stop 40 carried by a bracket 42 which also serves-as asupport for the-adjustable stop32. .The armature 24 has an opening 43 topermit the pawl 28 to engage the stop 40.; 1

The electromagnet 20, 22 is energized from a suitable source ofcurrent,-shown as a battery 44, upon closure of a switch 46, this switchbeingv operated in any suitable mannenhas by a cam 48 which may bedriven from the. propeller shaftof the vehicle or may be driven by,any'cther part the number of revolutions of which are to be counted. I.

When the parts are in normal position, as indicated in Fig. 3, thearmature 24 is held in engagement with the stop 30 by the spring, 36.The spring 36 is made of suilicient strength to prevent movement of thearmature from its rest position due to the vibration which may beencountered, as well as to store up sufficient power to drive theodometer.

-When the switch 48 is closed to complete the circuit through the coil22 of the electromagnet, the armature moves downwardly on the idlestroke through the position shown in Fig. 1, in which the pawl 28 hassnapped over one tooth of the ratchet wheel l2. At this intermediateposition of the downward movement of the armature the pawl 28 engagesits down stop 40 and further move- 3 ment of the pawl 28 is thusarrested. The armature 28, however. may continue its downward movementuntil it strikes the rubber bumper 88, as shown in Fig. 2. Any vibratoryrebound of the armature from this rubber stop will not have any effectupon the pawl 28, since the latter is held in position by its stop 88.

Upon opening of the switch 48, the armature and parts associatedtherewith are returned to their normal positions, as shown in Fig. 3, bythe spring 36, and during such return movement the pawl 28 advances theratchet wheel l2 one tooth.

Since the driving force applied to the pawl 28 is derived solely fromthe spring 38, it will be clear that by selection of a spring of theproper strength, the driving motion of the pawl 28 can be atsubstantially any desired speed, and will be uniform throughout theuseful life of the apparatus, irrespective of changes in the voltage ofthe source 84.

By virtue of the fact that the armature stroke may be greater than thestroke of the pawl, and that the stroke of the latter is in a senseindependent of the armature stroke, it will be apparent that the ratchetwheel may have teeth of very fine pitch and yet be operated reliablythrough an angle corresponding to the pitch of one tooth without dangerof overthrow or failure to operate upon each pulse. The force applied bythe spring l8 to the pawl l6 should be relatively light, since this pawlmerely prevents reverse movement of the ratchet wheel and does not haveto apply any appreciable frictional force for the purpose of retardingoverthrow, as might be necessary were the driving pawl 28 positivelyconnected to the armature.

Since the ratchet wheel can be made of very fine tooth pitch, the amountof intermediate speed reducing gearing between the ratchet wheel and theunits order odometer dial can be reduced. Such decrease in the number ofgears required to obtain this speed reduction lessens the amount ofpower required to be applied, and this in turn makes it possible to usea less powerful wheel may be of fine pitch and the initial air gap maybe made small, thereby making it possible to reduce the size of theelectromagnet and to decrease the amount of power required for itsoperation.

While I have shown and described a preferred embodiment of my invention,it will be apparent that numerous variations and modifications thereofmay be made without departing from the underlying principles of theinvention. I therefore desire, by the following claims, to includewithin the scope of the invention all such variations and modificationsby which substantially the results of my invention may be obtainedthrough the use of substantially the same or equivalent means.

I claim:

1. In an electrical impulse counter, the combination of an electromagnethaving a winding for connection to a source of impulses to be counted, apivoted armature for said electromagnet, stops to limit the stroke ofthe armature, resilient means to move the armature away from theelectromagnet, a leaf spring secured to the armature between the pivotpoint and the electromagnet, a pawl at the free end of the leaf spring,a ratchet wheel engaged by said pawl, and an adjustable stop limitingthe movement of the free end of said leaf spring toward theelectromagnet so that the total movement oi the free end of said leafspring will move said pawl only a predetermined distance on the idlestroke.

2. In an electrical impulse counter, the combination of an electromagnethaving a movable armature, resilient means to move said armature awayfrom the electromagnet, stops to limit the stroke of the armature, aratchet wheel, a pawl engaging the ratchet wheel and resiliently securedto the armature so as to be resiliently moved with the armature as thelatter is drawn toward the electromagnet and to be positively moved bythe armature during a portion of the return stroke of the latter, and astop independent of the armature limiting the movement of the pawltoward the electromagnet so that the total movement of the pawl will beonly a predetermined distance on the idle stroke and less than the totalmovement of the armature in the same direction.

3. In an electromagnetically operated device,

I the combination of an electromagnet having a winding for connection toa source of pulses, an armature, resilient means for moving saidarmature away from the electromagnet, a ratchet wheel, a driving pawlengaging the ratchet wheel, a resilient lost motion connection betweenthe armature and the driving pawl, and means independent of the armaturefor limiting the stroke of the pawl as the armature moves toward theelec- REFERENCES CITED The following references are of record in thefile of this patent:

UNITED STATES PATENTS Name Date Cooper Apr. 26, 1938 Breitenstem Oct. 8,i940 Blattner Oct. 13, 1942 Obszarny July 6, 1943 FOREIGN PATENTSCountry Date Netherlands Dec. 15, 1933 Australia Dec. 18, 1940 NumberNumber

